This invention relates generally to turbine rotors, and, more specifically, to a cover plate for use with a turbine rotor to facilitate reducing dovetail leakage through the turbine wheel.
At least some known turbines include wheel assemblies coupled to rotors. Known wheel assemblies include a turbine wheel with a plurality of retaining slots defined therein that are sized and shaped to receive a turbine bucket, or blade, therein such that the buckets, or blades, are coupled to the wheel, and extend radially outward from the wheel. Within at least some known wheels, a gap may exist between the buckets and retaining slots. During turbine operation, fluid can leak through the gap rather than flow through the buckets and/or nozzle area. Such leakage is generally uncontrolled and decreases the overall turbine efficiency.
To facilitate reducing dovetail leakage, at least some turbine buckets include a coating put on the bucket dovetails to reduce uncontrolled leakage through the gaps. Although the coating reduces the size of the gap in operation, such coatings do not adequately control leakage. Moreover, such coatings may wear permanently when the turbine is on turning gear. Other known rotor assemblies include circumferential seals or sheet metal cover plates. However, such components generally provide only marginal turbine efficiency improvements.